®
I n s t r u c t i o n S h e e t
0 1 2- 0 77 4 9 B
Heavy Duty Galvanometer
SF-9500A
*012-07749*
Introduction
The PASCO Model SF-9500A Heavy Duty Galvanometer is a
rugged yet sensitive instrument designed specifically for stu-
dent experiments. It has a center-zero meter that ensures easy
determination of polarity, and three current ranges. A
“Push-To-Read” switch protects the meter during hookup by
shunting the current through an equivalent resistor. When per-
forming a null-current experiment, such as measuring resis-
tance using a Wheatstone bridge, it is easy to balance the
current using the 5 mA (milliampere) range, then stepping
down through the lower current ranges to very accurately
determine the point of zero current.
Operation
To zero the meter:
Place the meter in the position (vertical or horizontal) in which
it will be used. Disconnect the meter. Use a small, flat-blade
screwdriver to turn the Zero Adjust Screw (located on the case
below the meter) until the meter needle e is aligned with zero
on the scale.
.
To measure current:
1.
Connect the circuit between the negative terminal of the gal-
vanometer and the red input connector with a current rating
greater than the expected current.
2.
When the connections are made, and you are ready to mea-
sure the current, press and hold the PUSH TO READ but-
ton.
3.
Now read the current on the meter.
The current ranges displayed beside the input connectors refer
to the current value that will give a full-scale meter deflection.
For example, a meter reading of +40 in the 5 mA range indi-
cates a current of 4 mA flowing through the galvanometer. A
reading of –40 indicates that 4 mA of current is flowing in the
opposite direction.
PUSH
TO
READ
5 mA
500
m
A
SF-9500A
50
m
A
Galvanometer
40
0
20
20
40
0
CE
®
Zero
Adjust
Screw
NOTE: If the meter is zeroed in one position and the
position is changed, it may need to be zeroed again.
NOTE: It is a good idea to begin with the 5 mA range,
then step down to the lower ranges as required. The
meter is protected while you make the connections,
because the current does not pass through the meter.
Instead it passes through a parallel shunt resistor that h
as the same resistance as the meter.
Direction of positive
current flow
Current Flow
